Nearly every variation of the untz played in today’s festivals and clubs owes something to the recently departed legend Frankie Knuckles, the DJ and producer who helped foment the early, classic version of house in Chicago. But Knuckles wasn’t the only influential producer in this era, which spanned the Eighties and early Nineties. Here’s a look at 20 essential Chicago house records – by Knuckles and others – that serve as required listening for any devoted student of dance music.